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  1. 75gmck25

    Transmission cooler ideas

    Long Mfg. Low Pressure Drop (LPD) coolers are stacked plate coolers (same design as B&M) and them come in many sizes. Most have a low temp bypass that automatically lets trans fluid bypass the cooler until the fluid is up to operating temperature...
  2. 75gmck25

    Crate SBC 350 installation plan

    My old SBC had the factory lifting eyes already on it, so I used them in combination with a balancer bar. I took the distributor and carburetor off so I wouldn't crunch them in the process, but had all accessory drives (but no fan), the fuel pump, and the iron exhaust manifolds mounted on the...
  3. 75gmck25

    Power steering gear box

    I think the boxes cross between 1/2, 3/4 and 1 ton without any issue if it's the same year group (IIRC, 73-78 shaft ends are different than 79 and up) and the same drive (2WD vs 4 WD).
  4. 75gmck25

    Did the NP203 change internally between 1974 and 1977?

    In the past they used to sell an NP203 chainsaver kit, but I haven't seen one advertised in a long time. I assume it just helped take out the slack in a worn chain, but maybe there was more to it.
  5. 75gmck25

    Small Block choices: A feller has too many

    I think my choice would be #3, then maybe bore it out .030 and use pistons that would work well with 64cc Vortec or aluminum heads. With the right pistons you could get it to about 9.5 compression, which would work well with aluminum heads as a daily driver. Very easy 325+ horsepower, and...
  6. 75gmck25

    Did the NP203 change internally between 1974 and 1977?

    There were problems with the internal chain drive on early NP203's and they used a different width in later models. The info I found says: 1973 - 1978 --> 3/8 Pitch x 2-1/2 W x 98 Pitch 1978 - 1979 --> 1/2 Pitch x 2 W x 72 Pitch I don't know if the difference in chain size would affect any of...
  7. 75gmck25

    General Motor Swap Questions

    These are roller cam engines, so cam break-in is not needed, and idling them is less of a concern. Just get timing and carburetor set well enough so it runs smoothly, and then start the break-in by driving at various speeds and rpm to seat the rings. Follow their recommendations for break-in...
  8. 75gmck25

    Confusion on fuel and more.

    My truck has a ‘74 cluster becsuse I found one with a tach, so I assume my speedometer is the same as yours. When I first bought a new speedometer cable they sold me one that had a threaded piece on the speedometer end, and I managed to get it to stay behind the spring clip on the speedometer...
  9. 75gmck25

    putting in air conditioner

    The big, long heavy compressor is the A6, and they often fail and contaminate the entire system with black granules. It’s usually best to dump it. Two options I suggest: -Pro6ten, which is a Sanden that is repackaged as an exact replacement for the A6. However, you will still need the mounting...
  10. 75gmck25

    AC Troubleshooting 1976 GMC C15

    Did your truck originally have the large A6 compressor mounted on the driver's side? I had that on my '75 and they were infamous for internal failure and "Black Death" (actually granules of black material) that contaminated the entire system. IIRC, the R-12 charge for my original system...
  11. 75gmck25

    Regearing Advice... What do I need?

    The 4.10 14 bolt was a common gearing in early 70’s 3/4 and 1 ton squarebodies. I would search for one and just do a swap for the rear. You might even find the matching front axle, which would probably be a Dana 44, Find a 14 bolt without gov loc, since then it’s easier to add a limited slip...
  12. 75gmck25

    Crate SBC 350 installation plan

    So this is a 2WD Blazer? Just checking, since on a 4WD you usually install the transfer case and transmission first, and then drop in the engine. On my K25 I bolted everything on the engine except the carburetor, and then dropped it into place using, using the cross bar to level it. You...
  13. 75gmck25

    AC duct behind glove box

    Based on the grommet around the line, it’s probably the vacuum supply line that goes through the firewall and connects to the vacuum reservoir under the hood. I think the line running up to the cowl vent may also have a grommet around it.
  14. 75gmck25

    AC duct behind glove box

    It’s all GM hard vacuum line, but someone repaired the end using a short section of rubber hose. It should have colored stripes that identify which vacuum motor each line connects to. You can buy a roll of replacement hard line from Dorman, and most auto parts stores used to stock it in two...
  15. 75gmck25

    Oxygen sensor

    I am confused about what you have. You mention an Atomic EFI conversion, but then you have an existing 1 wire O2 sensor (from what system?). Install and wire the new sensor based on the directions from Atomic EFI. Just run the new wires for the sensor that came in the installation kit.
  16. 75gmck25

    88 suburban 350 rebuild questions.

    What is your goal for the engine ( what will you use the Suburban for), and what is your budget? Most significant weakness of the Gen 1 SBC is the smog-era heads. They have poor flow and low compression for high HP build. Very fixable, but starting out with a purchase of new heads can jack up...
  17. 75gmck25

    Oxygen sensor

    Sounds like your new sensor is a heated O2 sensor. Makes it much less sensitive to where its located in the exhaust pipe, since it does not rely on engine/exhaust heat to warm up. I assume the original O2 sensor was a simple 2 wire, with no heat. I don’t know how you make the conversion...
  18. 75gmck25

    Sbc 350 kick-down cable help

    This is what mine looked like with a 1406. Top cable is the throttle, and I think that at this point the throttle cable retainer did not snap properly into the bracket. Cable was later replaced. Fitting on the end of your kickdown cable seems way longer than mine. Have your tried using the...
  19. 75gmck25

    Edelbrock accelerator pump

    Sounds like there is a problem with the accelerator pump. For a part throttle stumble you also might want to try different step-up springs. Edelbrock has a kit with springs rated at 4-8” of vacuum, and I think a stock 1406 spring is a 5”. The spring’s vacuum rating determines when the carb...
  20. 75gmck25

    Fuseable link

    My ‘75 has an inline fuse for the high blower speed , and I think it’s 25 amps.
  21. 75gmck25

    How to tell if my NP203 has been converted to part time?

    I don’t think my ‘75 with TH350 and NP203 has a support rod. I’d have to crawl under there to see if there is a threaded hole for the rod.
  22. 75gmck25

    Anyone seen these big tanks on a C30?

    When I first got my ‘75 K25 it had a dealer made, dealer installed auxiliary tank. It fit in about the same place as a stock saddle tank, but was made of welded together flat plates, so no rounded corners. One convenience it had was a drain petcock in the bottom. You could open it up and...
  23. 75gmck25

    How to tell if my NP203 has been converted to part time?

    Most NP203’s were converted by one owner, who never passed on the directions to the next owner. The docs with the kit tell you a converted NP203 has to be run in the 4LOC position about once a month to ensure full lubrication of the chain, output seals, and other internal parts. The chain...
  24. 75gmck25

    Not good at ac I need help

    My '75 has a CCOT system, so I'm not as familiar with the POA systems they used 73 and 74. You may want to check the discharge pressure cutout switch, which should be mounted into the hard line near the A/C box and blower motor. This switch prevents the A/C from turning on if pressure is too...
  25. 75gmck25

    "Overheating" --> Now Fuel Delivery Issue --> Dirty Tank?

    My ‘75 K25 has a 3 port pump, so they were used quite early. Return line goes back to the 6 port solenoid under the truck, and both supply and return are switched. Circulating fuel back through the return lines cools it down. Buy several feet of SAE J30R7 (low pressure) or SAE30R9 (high...

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